Dynamic range is one of the most important parameter in complementary metal-oxide-semiconductor (CMOS) image sensors. For example, dynamic range of natural scenes that we see in daily life is over 120 dB. Unfortunately conventional solid-state image sensors only cover 60˜70 dB at most without any special techniques. Conventional approaches to achieve high dynamic range (HDR) (i.e., a dynamic range above 70 dB) typically result in significant sacrifice with respect to pixel size, fill factor, and power consumption. This may limit the application of CMOS image sensors for portable devices or wireless sensor networks in which the chip area, bandwidth, and power consumptions are restricted.
Many applications require capturing an image of fast moving objects without distortion. Example applications are surveillance systems, traffic cameras, robotic visions, destruction testing, and scientific experiments. In some applications like automotive or outdoor surveillance systems, motion detection function is also important for controlling the vehicle or entire camera systems.
The motion detection function can be integrated in the imager and the motion information can be provided at extremely high speed. However, when the illumination is high (i.e., in the HDR domain), motion detection is unavailable with the conventional motion detection schemes. This is because the pixel is saturated in high illumination; therefore, both the HDR imaging scheme and the motion detection scheme cannot be integrated simultaneously in the single chip.